Ice dam risk in Two Rivers, WI
Will your roof get ice dams in Two Rivers, WI?
26.6 dam days a winter
High risk. On an ordinary house in Two Rivers, conditions for an ice dam come on about 26.6 days in a normal winter, mostly in February and January.
Two Rivers averages 46 inches of snow a year and about 78 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.
What your attic does to that number in Two Rivers
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 11.4 | Moderate |
| Typical, some insulation, not air-sealed | 26.6 | High |
| Older or poorly insulated, warm attic | 45.6 | Severe |
Sealing and insulating a typical attic takes out about 15.2 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 45.6 days.
Preventing ice dams on a Two Rivers roof
- Air-seal the attic floor: the gaps around the hatch, light fixtures, plumbing stacks and the top plates of interior walls. This is the fix that removes the cause, and it usually costs less than a season of contractor ice removal.
- Rake the bottom three or four feet of roof after any storm that leaves more than about six inches, from the ground with a roof rake.
- At the next reroof, ask for ice-and-water membrane under the shingles from the eave to at least 24 inches inside the wall line. It does not stop a dam; it stops the leak when one forms.
Which to spend on first: air sealing or heat cable.
Two Rivers winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 14.8 | 22.9 | 9.2 |
| February | 11.3 | 23.5 | 8.9 |
| March | 5.7 | 13.6 | 3.5 |
| April | 1.9 | 1.5 | 0.1 |
| October | 0.2 | 0.1 | 0.0 |
| November | 2.2 | 2.6 | 0.5 |
| December | 10.0 | 13.4 | 4.4 |
Two Rivers next to nearby towns
Two Rivers ranks 43 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Manitowoc, WI 6 mi, 26.2 days
- Bellevue, WI 28 mi, 29.3 days
- Sheboygan, WI 30 mi, 27.5 days
- Allouez, WI 31 mi, 29.3 days
- De Pere, WI 31 mi, 31.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Two Rivers, 1.0 miles from Two Rivers. A dam day is a day with snow on the roof and freezing at the eave while heat or sun melts the snow above it. This describes a normal winter, not this one.